(This paper was presented at AFMA’s annual symposium on 11 October 2006).
Soybeans and its by-products, Soybean Oil and Soybean meal continue to maintain a pace of increased production due to worldwide demand. The USDA World Agricultural Supply and Demand report for September 2006 states that…”for 2005/2006 strong demand for soybeans and soybean meal raises exports and crush and lowers ending stocks”.
Expectations for this year’s soybean crop are in the order of 83 million metric tons in the USA, 53 million in Brazil and 43 million in Argentina, the European Union and China being the primary importers with 41 and 31 million metric tons, respectively.
In the poultry industry, soybean meal is the main source of protein and amino acids in diets. Full-fat soybeans, due to its nutritional characteristics, high level and quality of protein (36 - 42%) and its high level of fat (18 - 22%), are an important source of protein and energy. Both products must be treated with heat in order to inactivate anti-nutritional factors, such as protease inhibitors (trypsin and chemotrypsin), hemagglutinins/ lectins and others. The inactivation of anti-nutritional factors by heating enhances nutrient digestibility.
However, overheating can lead to the breakdown of the protein in the grain or the meal, oxidation of sulfur in the sulfur amino acids, and the reaction of lysine with aldehyde groups, forming an unavailable complex, and also the reduction in metabolizable energy.
Considerable knowledge has been accumulated over the years to quantify the need and effect of heat treatment in soybean meal for animal feeding.
In contrast fairly limited information is available to address the specific issue of Quality Assurance (QA) specifications for commercial Full Fat soybeans in Poultry Feeding (Ruiz, et al., 2000). Sometimes it is convenient to assume the same QA specs for Soybean Meal as applicable to Full Fat Soybeans. However, Full Fat Soybeans are a different ingredient, with a different nutritional composition, and entirely different processing conditions. In addition to that, there are many different methods used to process Full Fat Soybeans.
The common objective is to denature the heat labile antinutritive factors therefore; the processing variables involved being temperature, moisture and time. Although direct steam treatment of soybeans (toasting) has been the traditionally used method, some other methods of heat treatment have proven equally effective, such as:
• Roasting: Intense dry heating. 110 - 168 °C depending on equipment used. It involves loss of about 30% of initial moisture.
• Fluidized-bed roasting/drying: variation from the previous one.
• Jet-Sploding: Dry heated air at 315 °C.
• Micronisation: roasting using infrared rays emitted by heated ceramic tiles. 118 - 220 °C.
• Extrusion: Dry friction (shear forces) or so called dry extrusion and wet steam injection (wet extrusion). Temperatures of 100 - 160 °C during a very short period of time (seconds).
The effects of processing of a given product may vary considerably with different procedures or conditions. An ideal thermal treatment process should inactivate antinutritional factors while simultaneously maintaining the bio-availability of essential aminoacids in the product (van Barneveld, 1993). The optimization of an efficient thermal process depends on the combination of temperature, time (duration), moisture content and particle size.
However, the optimal processing conditions may vary also with the different origin or cultivar of soybean being processed.
There are many studies in the literature which show that the different processing methods promote differences in nutrient utilization by Poultry (Mcnaughton and Reece, 1980; Garlich, 1988; Lee and Garlich, 1992; Parsons, 1992; Parsons and Baker, 1994; Jackson and Dalibard, 1995; Fernandez and Parsons, 1996; Sakomura, 1996; Penz, jr and Brugalli, 2000).
There is however fairly limited information available addressing the Quality Assurance parameters for Full Fat Soybeans in Poultry feeding.
The objective of this presentation will be 1) to understand variation in protein quality among soybean products such as Full Fat soybeans and Soybean meal, and 2) to understand the impact of that variation on broiler performance.
In order to understand variation we need to have data sets to study them.
Even though there is ample information available in the case of soybean meal from different origins, this is not the case for the Full Fat soybeans, Qin, et al. in 1996 concluded that steam toasting could effectively inactivate Trypsin Inhibitor Activity (TIA) and lectins in soybeans, with a concomitant reduction in the Urease Activity (UA), lectins and Protein Dispersability Index (PDI). At temperatures of 102 °C and 120 °C, TIA, UA, lectins and PDI decreased with the prolongation of heating time in a logarithmic pattern. These parameters however changed in different patterns for different origins of soybeans. Argentine soybeans needed less severe processing conditions than Chinese soybeans.
Ward, et al. in 1986 illustrated the effect of feeding Raw Full Fat Soybeans to Broilers (Table 1) and Zhang, et al. 1991 to commercial layers (Table 2).
Raw soybeans or undercooked soybeans have a very low digestible amino acids profile (Table 3) for utilization in the formulation of poultry diets.
Perilla, et al. in 1997 went further in attempting to determine the required temperature for wet extrusion to attain optimum broiler performance.
They concluded that the optimum heating temperature for wet extrusion of soybeans to be fed to chickens lies between 122 °C and 126 °C.
Temperatures below 122 °C results in underprocessing, while those above 126 °C may result in overheating.
Furthermore, they also concluded that the Trypsin Inhibitor Activity of the Full fat Soybeans is the best in vitro predictor of the nutritional value of soybeans for chickens, unless they are overheated, because the inhibitor activity is not detectable with overheating (Table 4).
These results were validated in a second experiment and, were also validated by determination of in vivo Digestible aminoacids coefficients (Ruiz, et al., 2004). Therefore, it was concluded that Trypsin Inhibitor activity and Urease activity can be utilized in practical prediction of Full Fat Soybeans Quality as it relates to chicken performance. Nevertheless, it was not possible to establish the value at which KOH Solubility correlates with the overprocessing of this ingredient.
It is extremely important for nutritionists in industry practice to use this type of tool to monitor the quality of the soybean products being utilized in poultry feeding, in order to predict and consistently manage animal performance in a commercial setting. Further research about the relationships between Quality Assurance Laboratory measurements of Soybeans and poultry performance is granted.
The references are available from the author or from AFMA.
The previous article is a special collaboration from AFMA South Africa
(Animal Feed Manufacturers Association) and their magazine AFMA Matrix.
We thank AFMA for their continuous, kind support!